Generally, a Time Division Duplex (TDD) radio repeater is a device for periodically performing on/off on transmission of each signal by using a frequency channel on a forward signal of a wireless terminal direction in a wireless base station and a backward signal of the wireless base station direction in the wireless terminal. The TDD radio repeater targets on providing a high-quality service to a terminal in a dead zone and is installed within a transmission section.
At this time, a synchronization acquisition procedure for synchronizing a forward/backward on/off operation timing is performed by using a general forward preamble. Since the preamble is structuralized to efficiently acquire synchronization in the TDD method and has identification (ID) on the base station and segment information, related information can be acquired through a signal process of a synchronization acquiring unit.
FIG. 1 shows a TDD radio repeater using conventional Adaptive Forward Error Correction (AFEC) and this configuration is disclosed by KR Patent Application No. 10-2007-0022436 (Applied on Mar. 7, 2007) by the applicants of the present invention.
As shown in FIG. 1, the TDD radio repeater using the conventional AFEC includes a donor antenna 100, a donor switching unit 102, a first down-converting unit 103, a synchronization acquiring unit 105, an AFEC 104, a first up-converting unit 106, a service antenna 109, a service band-pass filter 108, a service switching unit 107, a second down-converting unit 110 and a second up-converting unit 111.
The donor antenna 100 transmits/receives a signal to be relayed with the base station, i.e., a forward/backward relay signal. The donor band-pass filter 101 performs band on forward/backward relay signals transmitted/received through the donor antenna 100.
The donor switching unit 102 switches the forward relay signal from the donor band-pass filter 101 to the first down-converting unit 103 according to control of the synchronization acquiring unit 105, or switches the backward relay signal from the second up-converting unit 111 to the donor band-pass filter 101.
The first down-converting unit 103 down-converts the forward relay signal switched in the donor switching unit 102 into a baseband signal. The synchronization acquiring unit 105 acquires synchronization with the base station based on the forward relay signal down-converted in the first down-converting unit 103.
The AFEC 104 removes a feedback signal from the forward relay signal down-converted in the first down-converting unit 103 or the backward relay signal down-converted in the second down-converting unit 110 based on information from the synchronization acquiring unit 105 and controls gains of the forward/backward relay signals.
The first up-converting unit 106 up-converts the forward relay signal from the AFEC 104 into a relay signal of a high-frequency band again. The service antenna 109 transmits/receives a signal to be relayed with a terminal of a service region, i.e., a forward/backward relay signal.
The service band-pass filter 108 performs band filtering on the forward/backward relay signal transmitted/received through the service antenna 109. The service switching unit 107 switches the forward relay signal from the first up-converting unit 106 to the service band-pass filter 108 according to control of the synchronization acquiring unit 105, or switches the backward relay signal from the service band-pass filter 108 to the second down-converting unit 110.
The second down-converting unit 110 down-converts the backward relay signal switched in the service switching unit 107 into a baseband signal and transmits the baseband signal to the AFEC 104.
The second up-converting unit 111 up-converts the backward relay signal from the AFEC 104 into a relay signal of a high-frequency band again and transmits the relay signal to the donor switching unit 102.
Detailed configuration and operation of the AFEC 104 will be described in detail hereinafter with reference to FIG. 2.
FIG. 2 is a block diagram illustrating the conventional AFEC of FIG. 1 and forward and backward structures are the same.
As shown in FIG. 2, the conventional AFEC 104 includes a first automatic gain control unit 210, a first feedback signal detecting unit 208, a first reverse feedback signal synthesizing unit 206, a first feedback signal removing unit 204, a second automatic gain control unit 222, a second feedback signal detecting unit 220, a second reverse feedback signal synthesizing unit 218, a second feedback signal removing unit 216 and a control unit 214.
The first automatic gain control unit 210 automatically controls an output signal size of the forward relay signal to be relayed. The first feedback signal detecting unit 208 detects a phase and a size of a remaining feedback signal within the forward relay signal from the forward relay signal of the baseband inputted from the first automatic gain control unit 210 and the forward relay signal of the baseband inputted from the first down-converting unit 103, and updates the phase and the size of the feedback signal.
The first reverse feedback signal synthesizing unit 206 generates a reverse feedback signal to be used for removing the feedback signal within the forward relay signal by using the phase and the size of the forward relay signal of the baseband inputted from the first automatic gain control unit 210 and the feedback signal inputted from the first feedback signal detecting unit 208.
The first feedback signal removing unit 204 removes the feedback signal in the forward relay signal down-converted in the first down-converting unit 103 based on the reverse feedback signal from the first reverse feedback signal synthesizing unit 206, and transmits the forward relay signal to the first automatic gain control unit 210.
The second automatic gain control unit 222 automatically controls the output signal size of the backward relay signal to be relayed. The second feedback signal detecting unit 220 detects the phase and the size of the remaining feedback signal within the backward relay signal from the backward relay signal of the baseband inputted from the second automatic gain control unit 222 and the backward relay signal of the baseband inputted from the second down-converting unit 110, and updates the phase and the size of the feedback signal.
The second reverse feedback signal synthesizing unit 218 generates a reverse feedback signal to be used for removing the feedback signal in the backward relay signal based on the phase and the size of the backward relay signal of the baseband inputted from the second automatic gain control unit 222 and the feedback signal inputted from the second feedback signal detecting unit 220.
The second feedback signal removing unit 216 removes the feedback signal in the backward relay signal down-converted in the second down-converting unit 110 based on the reverse feedback signal from the second reverse feedback signal synthesizing unit 218 and transmits the backward relay signal to the second automatic gain control unit 222.
The control unit 214 controls each constituent element to transmit forward/backward relay signals after removing the feedback signal within the forward/backward relay signal to be relayed.
The conventional the AFEC 104 further includes a first automatic delay control unit 212 for preventing interactive interference between a feedback signal and a multipath signal. In the backward structure, a second automatic delay control unit 224 is included to be connected to the second automatic gain control unit 222.
The conventional AFEC operating as described above has the same structures in the forward/backward directions. However, since signal process methods are different in the forward/backward directions, AFEC for the forward direction and AFEC for the backward direction are respectively required for realizing the TDD radio repeater. Accordingly, there are problems that flexibility in arrangement of each constituent element is deteriorated and the size of the TDD radio repeater increases. In addition, consumption power, power loss and production cost increase and the AFECs having the same structure are inefficiently doubly used.